A plan being floated among Japan, the United States and South Korea is aimed at the complete denuclearisation of North Korea by the summer of 2020, diplomatic sources said on Tuesday, in a rejection of Pyongyang’s “phased, synchronised” approach in exchange for benefits.

The three countries are seeking an early end to Pyongyang’s development of nuclear weapons and missiles after past attempts allowed North Korea incremental incentives to halt its nuclear programme and led Pyongyang to buy time and further develop nuclear weapons, the sources close to Japan-US relations said.

In previous talks with Japan, the United States denied such an “action for action” approach had been pursued previously and said it envisioned a package agreement under which it will assure North Korea that it is not seeking regime change in exchange for Pyongyang’s complete, verifiable and irreversible denuclearisation, the sources said.

The United States also touched on a target date of around the summer of 2020 during the consultations, while other possible goals such as within 2018 or within a year after a US-North Korea agreement have also been floated among Japan, the United States and South Korea, the sources said.

Meanwhile, some Japanese, US and South Korean officials concede that making concessions to North Korea to a certain degree is unavoidable in order for Pyongyang to take steps towards denuclearisation, including disabling nuclear facilities and readmitting inspectors, the sources said.